I've found its usually more economical building your own. Done a few now over the years at different houses.
If you are trying to add an image you must have it hosted (on say imgur.com) and add the IMG tags to the pictures url.
Looking to build one myself (half to house a metal bin of coal, the other half for logs), interested in seeing how people have built theirs.
That looks great! Wish I had the space for something of that size.
OP, you've not said a budget or if you want a pre-built or go DIY. Responses so far are people building their own.
If you want to buy one pre-made / kit form the cheaper ones generally have thinner wood and fixings and the roof, if not supported correctly, may warp/sag/leak.
For the price difference in materials and time and faff for a DIY job compared to buying one made, it was worth doing the latter to me. Bought from here.
Solid frame of 2x2 and 3x3 wood.
It is a lovely garden feature on our patio so wanted it to look proper.
If it was to be placed out of the way somewhere I'd have knocked one up out of a few free pallets.